Your bra size is made up of two parts. The first number is your frame size (30, 32, 34, etc.) the second letter is your cup size (A, B, C, etc.).

To figure out yours, take a tape measure and measure snugly around your ribs, just under your bustline. If the measurement is on an odd number, add 5. If it's an even number, add 6 (for example, if you measure 26 around, you're a size 32). Total them up and that's your frame size.

Next, wrap the tape around your body again, this time measuring at the fullest part of your chest. Do this standing up straight, checking in a mirror that the tape is level. Subtract your original frame size from this measurement. Then check the chart below to figure out your cup size:

Bra Fitness: How to tell you’ve got the right stuff
You’re fairly sure you have the right band and cup size but something just doesn’t feel quite right. Let us assure you that there is one word that should describe any bra no matter what your chest size—comfortable. You have to wear one every day and you better make sure each and every one of them fits so well you’ll forget it’s even there. Well, almost.Fit problem: I’m spilling out. Cups that are too small need to be larger (and vice versa) but a changing the cup size can also change the band size. The C cup on a size 36 is the same as a B cup on a 38. If you go down a band size, you’ll go up a cup size. So try a going a step up and down on the band and cup size to get your perfect fit. And don’t forget about half sizes and “nearly” sizes from makers like Playtex.Fit problem: My band is riding up in back. Your bra band is too loose, your cups are too small or both. Try going up a cup size or down a band size. And remember that a large bust needs a wider, closer fitting band than smaller busts to provide proper support.Fit problem: My straps are sliding off my shoulders.The easiest thing to do is tighten them up using the adjustment on each shoulder strap. If you have very narrow shoulders or if they slope, look for more sports-bra type cuts that have wider straps placed closer to your neck.Fit Problem: My straps are digging into my shoulders. Your band is too loose band or cups your cups are too small. If your bust is larger, you also might want to look for a bra with wider straps.